Paediatric surgical trials, their fragility index, and why to avoid using it to evaluate results

Abstract

Background The fragility index has been gaining ground in the evaluation of comparative clinical studies. Many scientists evaluated trials in their fields and deemed them to be fragile, although there is no consensus on the definition of fragility. We aimed to calculate the fragility index and its permutations for paediatric surgical trials. Methods We searched pubmed for prospectively conducted paediatric surgical trials with intervention and control group without limitations and calculated their (reverse) fragility indices and respective quotients along with posthoc-power. Relationships between variables were evaluated using Spearman’s ρ. We also calculated S values by negative log transformation base-2 of P values. Results Of 516 retrieved records, we included 87. The median fragility index was 1.5 (interquartile range: 0–4) and the median reverse fragility index was 3 (interquartile range: 2–4), although they were statistically not different (Mood’s test: χ2 = 0.557, df = 1, P = 0.4556). P values and fragility indices were strongly inversely correlated (ρ = − 0.71, 95% confidence interval: − 0.53 to − 0.85, P < 0.0001), while reverse fragility indices were moderately correlated to P values (ρ = 0.5, 95% confidence interval: 0.37–0.62, P < 0.0001). A fragility index of 1 resulted from P values between 0.039 and 0.003, which resulted in S values between 4 and 8. Conclusions Fragility indices, reverse fragility indices, and their respective fragility quotients of paediatric surgical trials are low. The fragility index can be viewed as no more than a transformed P value with even more substantial limitations. Its inherent penalisation of small studies irrespective of their clinical relevance is particularly harmful for paediatric surgery. Consequently, the fragility index should be avoided.

An analysis of randomized controlled trials on anal fistula conducted between 2000 and 2020 based on the Fragility Index and Reverse Fragility Index

“…In general, studies in other surgical fields have also revealed low FI values [11]. Thus, in head and neck surgery [12] with 27 RCTs the FI was 1 (0–2.5), in urology [13] with 41 trials it was 3 (1.4–5), and in paediatric surgery [14] and ophthalmology [15] with 156 attempts it was 2 (0–48).…”